ChatSim Unlimited is a global roaming SIM card with an unbeatable price: $12 for the SIM, plus $12 per year for unlimited messaging through various chat apps. I tried it in two European countries and found it delivered on its promises in both Greece and Spain, as well as at home in New York City. But its very limited list of supported apps and functions means the service will have limited appeal here in the US.

How and Where It Works

ChatSim works in 150 countries. It technically gives you a number on the British island of Jersey, but nobody can call it. Jersey Telecom, the carrier that ChatSim uses, enables a bunch of other global SIM solutions as well, such as Contiki eKit and Telestial Passport.

After you pop in the SIM in an unlocked phone, you have to manually set your phone's data APN to ChatSIM's settings, and turn off background data usage and automatic app updates in your phone's settings screen. If you don't, you may find your SIM card ends up being "blocked," requiring you to log into ChatSim's site on a Wi-Fi connection to unlock it. I didn't run into that problem, and my SIM worked fine for two weeks.

As promised, loading and sending messages in WhatsApp was swift, but voice calls and Web requests simply wouldn't connect. ChatSim points out that you can make outbound voice calls through Facebook Messenger and Whatsapp if you need to.

But ChatSim's list of supported messengers doesn't match up well with how Americans send messages, which is primarily via text. According to eMarketer, only 44 percent of North American mobile phone users use any chat apps at all. ChatSim doesn't support texts, but works with chat apps including BBM, Facebook Messenger, Hike, Imo, Kakao Talk, LINE, QQ, Telegram, and WeChat. That's a very Asia-focused list. It doesn't support three out of the five most-used chat apps in the US according to Statista: iMessage, Skype, and Yahoo. It also doesn't support Snapchat or Twitter DMs. Of ChatSim's list, Facebook Messenger is probably the most popular option for Americans.

If you want to send or receive multimedia messages or make voice-over-IP (VoIP) calls, you have to buy additional credits. For most countries, ChatSim charges €10 (about $11) for 40MB of data, or €25 (about $27.50) for 100MB. That then gets used by your photo messages and VoIP calls. ChatSim estimates that a 40MB recharge gives you 200 photos, 40 videos, or 80 minutes of calling. ChatSim does not offer standard Internet access, so there's no web, no maps, and no streaming. That means you can send Facebook Messages, but you can't update your Facebook status; for that, you'll have to go look for Wi-Fi.

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Should You Switch to ChatSim?

ChatSim is best for Verizon and prepaid service users. Verizon doesn't have a inexpensive international roaming plan (its minimum $25 per month still charges by the text, although you also get 100MB of data), and all Verizon phones are unlocked. 

Chat apps like Whatsapp use very little data, so they work very well with Sprint and T-Mobile's free 2G roaming. If you have a Sprint Open World or T-Mobile Simple Global plan, you may not need ChatSim (and you get texting, to boot.) AT&T's $30 Passport includes unlimited texting and 120MB of data, which is a lot of Whatsapp messaging. 

Conclusions

If your friends use one of ChatSim's supported apps, it's a delightfully inexpensive way to keep in touch. On our trip, I used ChatSim to offer my daughter a quick, easy way to text me when I was at work, and it worked perfectly. I'd absolutely recommend it for families who give their kids phones as a way to keep in touch on journeys. But it's not a general purpose solution for Americans, even those who only use messaging. At the very least, ChatSim needs to support our most-used apps.